1. Field of the Invention
The present invention relates to grafted starch polymer solutions and, more particularly, to a material which reduces the viscosity of grafted starch copolymer solution. Furthermore, the present invention relates to a process of preparing lower viscosity grafted starch polymer solutions using the viscosity reducing materials of the present invention and the use of these low viscosity grafted starch polymer solutions as dry strength additives for fibrous substrates such as paper.
2. Discussion of the Prior Art
Starch based polymers, more particularly grafted starch polymers, have been found useful as adhesives, coatings, and resins useful for improving the properties of paper. Starch based polymers are applied as solutions, typically aqueous. The use of starch based polymers has been hindered because of the generally high viscous nature of the solutions containing such starch polymers. Various procedures to reduce the viscosity of a starch based polymer solution have been utilized. One such method involves raising the temperature of the starch solution. Another method is to reduce the overall percent solids of the starch polymer in solution. Both of these alternatives are economically disadvantageous. Heating and maintaining the solution at an elevated temperature requires the use of complicated equipment. The use of more dilute solutions of starch polymers is disadvantageous since it would require the application of larger amounts of solution to obtain the necessary amount of polymer application and would also require the transportation of more dilute solutions which is expensive.
Another method of reducing the viscosity of a starch based polymer solution is through the use of enzyme modified starch which reduces the overall viscosity of the starch solution. While this method is advantageous for certain uses, it is sometimes desirous and essential that the starch not be modified with enzyme prior to use.